As shown in the figure, in the quadrilateral ABCD, points E and F are on BC and CD respectively, and ab = AE = AF = ad = BC = CD = EF, then the degree of ∠ C

As shown in the figure, in the quadrilateral ABCD, points E and F are on BC and CD respectively, and ab = AE = AF = ad = BC = CD = EF, then the degree of ∠ C

Connecting a and C, easy to prove AC ⊥ ef
Therefore, ACF + EFC = 90 degree
And ∠ EFC + ∠ AFD = 180 ° - 60 ° = 120 °
Therefore, d = AFD = ACF + 30 degree
∠DAC+∠ACF+∠D=∠ACF+∠ACF+∠ACF+30°=180°
∠ACF=50°
∠C=2∠ACF=100°

In the quadrilateral ABCD, point E is the midpoint of BC, point F is the midpoint of CD, and AE is vertical to BC, AF is vertical to CD

Connect AC
Because AE is perpendicular to BC, point E is the midpoint of BC
So AB = AC
Because AF is perpendicular to CD, point F is the midpoint of CD
So AC = ad
So AB = ad

In the quadrilateral ABCD, point E is the midpoint of BC, point F is the midpoint of CD, and AE ⊥ BC, AF ⊥ CD
xie xie la yao qiu ju ti yidian o.

Connect AC
Be = EC, AE ⊥ BC, ab = AC
CF = FD, AF ⊥ CD, ad = AC
So AB = ad